1. Technical Field
The present invention relates to a relay module for relaying the wiring of a motor circuit, and more specifically, to a relay module used in place of an electromagnetic switch used when an induction motor is connected.
2. Description of the Related Art
When an induction motor is to be additionally connected to a machine tool, an electromagnetic switch must be mounted on the distribution panel of the machine tool and the induction motor must be connected to the machine tool through a wiring additionally connected to the electromagnetic switch. Alternatively, as described below, when the electromagnetic switch is mounted between two terminal bases previously provided for the distribution panel, wirings are additionally connected between the two terminal bases and the electromagnetic switch to connect the induction motor. The connection of the induction motor will be described with reference to FIG. 6.
FIGS. 6(A) and 6(B) are diagrams explaining the induction motor connected by the above conventional method, wherein FIG. 6 (A) shows the state that the induction motor is not connected and FIG. 6 (B) shows the state that the induction motor is connected, respectively. In FIG. 6 (A), a distribution panel 20 is connected to, for example, an I/O circuit of a programmable machine controller (PMC) of a numerically controlled machine tool. The distribution panel 20 has two rows of terminal bases 21 and 22 spaced apart from each other. When an induction motor 30 is to be connected to the distribution panel 20, an electromagnetic switch 100 must be disposed between the terminal bases 21 and 22 to turn ON/OFF power supplied to the induction motor 30, as shown in FIG. 6 (B). Therefore, the respective terminals 21a, 21b, 21c of the terminal base 21 must be connected to the primary terminals 100a, 100b, 100c of the electromagnetic switch 100 through additional wires and the secondary terminals 100d, 100e, 100f of the electromagnetic switch 100 must be connected to the respective terminals 22a, 22b, 22c of the terminal base 22 through additional wires.
Nevertheless, since this induction motor 30 is optionally provided for the machine tool, whether it is to be mounted or not is often altered even in the time from the placement of an order from a user to the shipment of the machine tool. Moreover, several tens of the induction motor 30 may be used in a single machine tool. Consequently, a problem arises in that a job for mounting or dismounting the induction motor 30 is increased even during a time until a single machine tool is shipped and each time the motor is mounted or dismounted, a job must be carried out to mount and wire the above electromagnetic switch 100 or dismount it and remove its wiring.
Note, since the electromagnetic switch 100 is expensive, when the induction motor 30 is to be removed, the electromagnetic switch 100 and the wiring thereof are removed accordingly and restored to the state shown in FIG. 6 (A).
As described above, it is very time-consuming to ship a single machine tool. Further, when a user actually uses the machine tool shipped thereto, he may mount or dismount the induction motor 30, and in this case a similar job must be carried out and this job is time-consuming in the same way.